This invention relates to a sprocket wheel for driving and/or guiding a drive chain for a scraper-chain conveyor or a mineral winning machine such as a coal plough. The invention is particularly concerned with a sprocket wheel for use with a drive chain having chain links made from rod of circular cross-section.
The sprocket wheel of this type has a plurality of equi-spaced circumferential teeth. The adjacent teeth define pockets for the reception of the links of a drive chain. Each of the teeth is of two-part construction, the sprocket wheel being formed with a central circumferential groove which passes through all the teeth thereby defining their two-part construction. Alternate links of the chain lie within the pockets as the chain passes round the sprocket wheel, and the remaining links (which lie substantially at right-angles to the first-mentioned links) are accommodated in the groove. The two ends of each pocket are defined by flanks formed on the mutually-facing portions of the two parts of each of the teeth defining that pocket. The tooth flanks at the two ends of each pocket converge slightly, and define chain link bearing faces.
In a known sprocket wheel of this type, the tooth flanks formed at each end of each pocket are constituted by bearing surfaces which are inclined to one another at an angle of about 90.degree.. The arrangement is such that the chain links contact the tooth flanks at points which are disposed at a predetermined distance from the central circumferential groove. In this way, it is possible to avoid excessively high punctiform loading of the tooth flanks immediately adjacent to the groove. If such loading were to occur, it would result in heavy wear of the chain links, and may lead to the formation of what are known as "parsons' noses". This sprocket wheel is described in DE-AS No. 2735792.
The disadvantage of this sprocket wheel is that, owing to the unavoidable variations in chain link size which occur during manufacture of chains made from rod of circular cross-section, excessively high punctiform loading can still occur, and this can lead to dangerous notching of the chain links. Moreover, even where the points of contact of the chain links with the tooth flanks are intended to lie at the predetermined (safe) distance from the edge of the central circumferential groove in the sprocket wheel, the points of contact can move nearer the groove for chain links of different sizes.
The aim of the invention is to provide a sprocket wheel which does not suffer from these disadvantages.